Cleaning elements, such as bristles, are used in many personal-care and commercial implements, such as, e.g., those used in oral-care and beauty-care applicators, as well as industrial brush products. Generally, a bristle, or a filament, is a thin flexible fiber terminating with a free end, or tip, when it is incorporated into a finished implement, such as a brush. Examples of such implements, comprising a plurality of fibers, include, without limitation, toothbrushes, mascara and other cosmetic brushes, painting brushes, and various cleaning brushes.
In many of those applications, a brush implement is designed to perform at least one of the two functions: (1) a delivery or application of a material to an object and (2) a removal of a material from an object. In many instances, the efficacy with which these functions are performed by an implement is highly influenced by the surface characteristics of the filaments.
In the field of oral care, for example, it is well known that regular tooth brushing with a dentifrice is an effective means of reducing or preventing tooth decay, periodontal disease, removing food debris, and massaging the gums. Commercially available toothbrushes typically include monofilament or co-extruded filament bristles mounted on a plastic support. The thin flexible bristles are smooth elements of which the ends are cut off at right angles and are often rounded to form dome-like tips. Most commercial dentifrice include a mild abrasive particles ranging from about 10% to 25% by weight to improve the composition's ability to remove adherent soiling matter, to free accessible plaque, to dislodge accessible debris and to eliminate superficial stain from teeth. But the smooth, dome-like tips are not designed for effective pick up and utilization of the particles in dentifrice. Nor can they have effective abrasion efficiency against dental plaque. When no abrasive particle is present, filaments with lesser degree of end-rounding are believed to be more effective for cleaning. Their hard peripheral edges, however, can lead to excessive damage in both hard and soft tissues in the oral cavity.
Multiple attempts to address these and similar problems have been made. For example, U.S. Pat. No. 6,138,314 is directed to a toothbrush having an improved cleaning and abrasion efficiency. The bristles in that toothbrush contain longitudinal channels having a depth sufficient to entrap a quantity of abrasive particles such that during brushing with toothpaste, contact between the channel-entrapped abrasive particles and the surfaces of the teeth is improved. U.S. Pat. No. 3,613,143 is directed to a toothbrushes having abrasive impregnated bristles of two cross-section designs, i.e., to generally circular and polygon with the latter described as having longitudinal groove arrangements. U.S. Pat. No. 4,167,794 is directed to rounded bristles having shovel-like distal ends for more effective plaque removal. U.S. Pat. No. 4,958,402 is directed to fiber-flocking synthetic bristles that can retain and more effectively distributing a substance on the surface to be treated. U.S. Pat. No. 3,032,230 is directed to bristles having a polygon cross-section having at least two acute angles that impart a “scraping” effect on the teeth. U.S. Pat. No. 3,214,777 is directed to bristles having a rectangular cross-sectional area. U.S. Pat. No. 4,993,440 is directed to a cosmetic brush comprising bristles having capillary channel extending from the base to the tip of the bristles. The channel has a V-shaped or U-shaped cross section designed to hold the mascara.
Coextruded monofilaments having a core made of one material and a sheath made of another material are also known. For example, U.S. Pat. No. 5,770,307 is directed to a coextruded monofilament having a core material made of a first resin and a sheath material made of a second resin, with the second resin being different from the first resin, and a pocket formed in the end of the monofilament. The purpose of the pocket is to hold a material, such as a cleaning material, so that the cleaning material in the monofilament has a longer contact with the surface to be cleaned than if the cleaning material was on the rounded end of a conventional monofilament. For example, if the coextruded monofilament is used in a toothbrush bristle, the pocket will hold toothpaste in contact with a tooth longer than a coextruded monofilament with a conventional rounded end. The pocket formed in the end of a coextruded monofilament can be made by chemical or mechanical means, or a combination of chemical and mechanical means. While the filament having a pocket, disclosed in this patent, appears to allow retention of a cleaning material inside the pocket, the structure of the disclosed filament itself does not appear to offer additional abrasion efficiency.
The present disclosure is directed to further improvements of the filaments.